Polyimides used as microelectronic coatings

ABSTRACT

New polynuclear aromatic diamines, such as 2,2′-di-(p-aminophenoxy)-biphenyl, a process for their manufacture and their use as polycondensation components for the manufacture of polyamide, polyamide-imide and polyimide polymers are described. The polymers obtained with the aromatic diamines according to the invention are readily soluble and can also be processed from the melt and are distinguished by good thermal, electrical and/or mechanical properties.

This application claims the benefit of Provisional Application No.60/117,960, filed Jan. 29, 1999.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed to polyimides having very lowdielectric constants, low coefficients of thermal expansion, improvedthermal stability and excellent solubility in conventional organicsolvents. More particularly, the present invention is directed to amethod of coating microelectronic aparatii, components, parts andelements with a polyimide film, the polyimide film comprising thepolymerization product of a fixed aromatic diamine or fixed aromaticdianhydride having a fluorine-containing substituent and a2,2′-disubstituted dianhydride and 2,2′-disubstituted diamine,respectively. The polyimides of the present invention are easilyprocessed in many conventional organic solvents and may be cast intothin films that are suited for coatings in the microelectronicsindustry.

BACKGROUND OF THE INVENTION

Polyimides are useful as components that require excellent thermal,electrical and/or mechanical properties. For general discussion ofpolyimide preparation, characterization and applications, one can referto Polyimides, Synthesis, Characterization and Applications, L. Mittal,ed Plenum, N.Y. 1984.

Polyimides based on pyromellitic dianhydride and various organicdiamines are disclosed in U.S. Pat. No. 4,485,140 to Gannett et al.Polyimides based on diamines such as 2,2′-di-(p-aminophenyloxy)-diphenyland various dianhydrides are disclosed in U.S. Pat. No. 4,239,880 toDarms. Harris et al., in U.S. Pat. No. 5,175,242, has disclosed thepreparation of soluble polyimides based on 3,6-diarylpryomelliticdianhydride and various diamines including the diamines of the presentinvention.

Aromatic polyimides are synthesized by the polymerization of an aromaticdianhydride with an aromatic diamine. The presence of the aromatic andimide rings in the polyimide chemical repeating units result in anaromatic polyimide possessing chain rigidity and linearity. The aromaticpolyimide structures possess high thermal stability, outstandingmechanical properties and excellent chemical resistance.

Most aromatic polyimides, however, are insoluble in conventionalsolvents and processing is difficult. The insolubility of polyimidesoriginates from their high aromaticity, their rigid imide structure inthe polymer backbone, as well as the formation of the inter andintramolecular charge transfer complexes and the ordered structuresresulting form chain packing of the molecules.

The polyimides derived from the above cited references lack consistencyin satisfactory properties to be used as high clarity, low dielectricconstant coating materials or as high compression strength fibers orfabrics. Therefore, is it desirable to develop polyimides that havelower dielectric constants, higher coefficients of thermal expansion,good thermal stability and that are soluble in conventional organicsolvents, thus allowing processing in the imide form to avoid manyproblems associated with handling poly(amic) acid precursors.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide polyimidecoatings having excellent solubility in conventional organic solvents.

It is a further object of the present invention to provide polyimidecoatings having a low dielectric constant.

It is a further object of the present invention to provide polyimidecoatings having high coefficients of thermal expansion.

It is a further object of the present invention to provide polyimidecoatings having excellent thermal stability.

The present invention therefore provides an integrated circuitcomprising an integrated circuit and an insulating layer disposed onsaid integrated circuit, wherein said insulating layer is a polyimidefilm that is the polymerization product of an aromatic diamine havingthe general formula (I):

and an aromatic dianhydride having the formula (II):

wherein R is an organic substituent selected from the group consistingof CF₃, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5-bis[(m-trifluoromethyl) phenyl]; or thepolymerization product of an aromatic dianhydride having the generalformula (III):

and an aromatic diamine having the formula (IV):

wherein R is a substituent selected from the group consisting oftrifluoromethyl, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5′-bis[(m-trifluoromethyl) phenyl].

The present invention further provides an insulated electricallyconductive component comprising an electrically conductive component;and an insulating layer that is the polymerization product of anaromatic diamine having the general formula (I):

and an aromatic dianhydride having the formula (II):

wherein R is an organic substituent selected from the group consistingof CF₃, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5-bis[(m-trifluoromethyl) phenyl]; or thepolymerization product of an aromatic dianhydride having the generalformula (III):

and an aromatic diamine having the formula (IV):

wherein R is a substituent selected from the group consisting oftrifluoromethyl, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5′-bis[(m-trifluoromethyl) phenyl].

The present invention further provides a method of coating an integratedcircuit comprising the steps of preparing a polyimide comprising thepolymerization product of an aromatic diamine having the general formula(I):

and an aromatic dianhydride having the formula (II):

wherein R is an organic substituent selected from the group consistingof CF₃, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5-bis[(m-trifluoromethyl) phenyl]; or thepolymerization product of an aromatic dianhydride having the generalformula (III):

and an aromatic diamine having the formula (IV):

wherein R is a substituent selected from the group consisting oftrifluoromethyl, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5′-bis[(m-trifluoromethyl) phenyl];applying the polyimide dispersed within the organic solvent to thesurface of the integrated circuit forming a thin insulating layer orfilm on the surface of the circuit; and heating the integrated circuitwith the insulating polyimide layer or film disposed thereon to atemperature sufficient to evaporate the organic solvent and to cure thepolyimide.

DETAILED DESCRIPTION OF THE INVENTION

It has now been discovered that the use of certain polyimides that areuseful for insulating electronic and microelectronic components givesrise to unexpectantly superior properties. Namely, the polyimides usedin this invention have been found to exhibit superior dielectricconstants, coefficients of thermal expansion, and thermal stability,even when compared to similar polyimide compounds. Additionally, thepolyimides used in this invention are advantageously soluble in commonorganic solvents and, therefore, are easily processed and used forinsulating electronic and microelectronic components.

The polyimides used in this invention are selected from the group ofpolyimides that are the polymerization product of polymerization productof an aromatic diamine having the general formula (I):

and an aromatic dianhydride having the formula (II):

wherein R is an organic substituent selected from the group consistingof CF₃, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5-bis[(m-trifluoromethyl) phenyl].

Also, the polyimides used in this invention are selected from the groupof polyimides that are the polymerization product of an aromaticdianhydride having the general formula (III):

and an aromatic diamine having the formula (IV):

wherein R is a substituent selected from the group consisting oftrifluoromethyl, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5′-bis[(m-trifluoromethyl) phenyl]. Ithas now been found that modifications of the dianhydride and diaminemonomers to include fluorine-containing substituents results in apolyimide film useful for coating microelectronic components, parts,elements, connectors and aparatii, having very low dielectric constants,improved coefficients of thermal expansion (CTE), improved thermalstability and excellent solubility in many common organic solvents.

The foregoing polyimides can be prepared in accordance with thetechniques and teachings of U.S. Pat. Nos. 5,395,918 and 5,071,997, andtherefore both of these patents are incorporated herein by reference.

Notably, the polyimides used in this invention can be polymerized byusing a one step polymerization method. This ability makes thepolyimides employed in this invention extremely useful as coatings,layers or films for electronic or microelectronic applications.

The prior art coating methods involve a three step process includingcoating a microelectronic components, usually computer chips, with apoly(amic) acid precursor coating material, heating the poly(amic) acidprecursor coating material to a temperature sufficient to burn off theexcess organic solvent followed by a second heating step to cure thepoly(amic) acid prescursor into a polyimide. The coating method of thepresent invention is an improvement over the prior art in that thepolyimide is highly soluble in most common organic solvents and,therefore, a solution containing the polyimide may be coated on thecomponents in one step, without the steps further curing the poly(amic)acid precursors into polyimides.

As described above, is it desirable to develop polyimides that aresoluble in common organic solvents to allow processing in the imide formin order to avoid many problems associates with handling poly(amic) acidprecursors. This is especially important in microelectronic coatingapplications, where the imidization conditions for PAAs used duringprocessing can dramatically affect their ultimate material properties.

The present invention is an improvement over the prior art methods ofcoating microelectronic components in that the polyimides disclosedexhibit excellent solubility in many common organic solvents withoutsubstantially decreasing the rigidity of the polyimide backbonestructure. This is especially important for applications where theimidization condition of poly(amic) acid precursors can dramaticallyeffect structure, morphology and final material properties. Maintainingthe polyimide backbone structure minimizes reduction in thermal andmechanical properties. The polyimides used in the present invention aresoluble in most common organic solvents including, but not limited to,acetone, cyclopentanone, tetrahydrofuran (THF), N,N′-dimethylacetamide(DMAc), N,N′-dimethylformamide (DMF), N-methylpyrrolidone (NMP),p-chlorophenol and m-cresol.

The polyimide coatings of the present invention are soluble in manycommon nontoxic solvents and can be readily cast into flexible, toughfilms having low dielectric constants, high coefficients of thermalexpansion and high thermal stability. A one step polymerization methodhas been previously developed for organo-soluble aromatic polyimides. Inthis procedure, the dianhydride and diamine are dissolved and stirred at180–200° C. in refluxing high boiling m-cresol or p-chlorophenol. Thewater generated by the imidization is usually distilled off from thereaction mixture. Although the formation of the polyimide is most likelyto proceed via poly(amic) acid precursors, these precursors are onlypresent as extremely short-lived intermediates. Imidization occurssimultaneously with the chain propagation reaction or shortlythereafter. Therefore, the one step imidization process of the presentinvention avoids the uncontrollable structure, morphology and propertiesassociated with the two-step polymerization route.

As described above, polyimides of the present invention be used ascoating or films for various microelectronic components and may beintegrated with other electronic components acting as an interlayerdielectric in integrated circuits. In evaluating the usefulness ofpolyimides as dielectric coatings, layers and films, physical propertiesof polyimides, namely the dielectric constant (ε), the coefficient ofthermal expansion (CTE), thermal stability, and solubility must beevaluated.

In fact, the polyimides used in this invention have been found toexhibit a dielectric constant that is less than 2.8, advantageously lessthan 2.7, and even more advantageously less than 2.5. Further, thepolyimides used in this invention have been found to exhibit acoefficient of thermal expansion that is greater than about 23×10⁻⁶/°C., advantageously greater than about 42×10⁻⁶/° C., and mostadvantageously greater than about 54×10⁻⁶/° C.

In one embodiment, the present invention is directed toward anintegrated circuit that includes at least one insulating layer that isformed from the polyimides defined hereinabove. These polyimide layersof films have a thickness of between about 10 and about 1000 microns,preferably about 10 to about 500 microns and most preferably about 10 toabout 100 microns. Microelectronic computer chips are well known in theart and the selection of any one specific electronic configurationshould not limit the scope of the present invention. For a detaileddiscussion of the design, manufacture and electrical, thermal andmechanical properties of microelectronic computer chips and relatedelectronic or microelectronic circuits, one can refer to ElectronicMaterials Handbook, Volume 1. ASM International, (1989), which isincorporated herein by reference.

In one embodiment of the present invention, the polyimides used are thepolymerization product of a fixed fluorine substituent-containingdianhydride, namely 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropanedianhydride (6FDA) and one of a series of4,4′-diamino-2,2′-disubstituted biphenyls. The4,4′-diamino-2,2′-disubstituted biphenyls are selected from the groupconsisting of 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)-biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (O6FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (M6FDPBZ) and4,4′-diamino-2,2′bis[3,5-bis(trifluoromethyl)phenyl] biphenyl(M12FDPBZ).

In another embodiment of the present invention, is the polymerizationproduct of a fixed fluorine-containing substituent diamine, namely4,4′-diamino-2,2′-bis(trifluoromethyl) biphenyl (PFMB) and one of aseries of 2,2′-disubstituted-4,4′,5,5′-biphenyltetracarboxylicdianhydrides. The 2,2′-disubstituted-4,4′,5,5′-biphenyltetracarboxylicdianhydrides are selected from the group consisting of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M12FDPBPDA).

In another embodiment, the present invention is directed to anelectrically conductive component including-an insulating polyimide filmor layer, the polyimide film or layer being prepared as discussedhereinabove.

In another embodiment, the present invention also provides a method ofcoating an integrated circuit comprising preparing a polyimide film, thepolyimide film being prepared as described hereinabove; applying thepolyimide to the surface of the integrated circuit forming a thininsulating layer or film on the surface of the integrated circuit; andheating the integrated circuit having the polyimide film disposedthereon to a temperature sufficient to evaporated the excess organicsolvent and to cure the polyimide.

Methods of applying the polyimide to the integrated circuit include, butare not limited to, spraying, dipping, spin-coating, brush-coating andflow-coating.

GENERAL EXPERIMENTAL

Preparation of Polyimides

As described above, 6FDA-based, PFMB-based and DMB-based polyimides weresynthesized according to the methods disclosed by Harris et al., U.S.Pat. Nos. 5,395,918 and 5,071,997, the entire disclosure of each patentincorporated herein by reference. Acetone, chloroform, andtetrahydrofuran were purchased from Fisher Scientific Co. 2-Pentanone,cyclopetanone, cyclohexanone, methyl ethyl ketone (MEK),γ-butyrolactone, propylene glycol methyl ether acetate (PGMEA),N,N′-dimethylacetamide (DMAc), N,N′-dimethylformamide (DMF),dimethylsulfoxide (DMSO), N-methylpyrrolidone (NMP) and m-cresol werepurchased from Aldrich Chemical Company. DMSO, NMP, DMAc and m-cresolwere distilled under reduced pressure prior to use.

The dielectric constants for 6FDA-based polyimide films was determinedusing ASTM-150 method at 1 MHz on 6FDA-based polyimide films having athickness of 10 to 40 microns. The dielectric constants were determinedfor 6FDA-based polyimide films comprising the polymerization product of6FDA and 4,4′-diamino-2,2′-dichlorobiphenyl (6FDA-DCB, comparative),4,4′-diamino-2,2′-dibromobiphenyl (6FDA-DBB, comparative),4,4′-diamino-2,2′-diiodobiphenyl (6FDA-DIB, comparative),4,4′-diamino-2,2′-dimethylbiphenyl (6FDA-DMB, comparative),4,4′-diamino-2,2′-dicyanobiphenyl (6FDA-DCN, comparative),4,4′-diamino-2,2′-bis(p-methylphenyl)biphenyl (6FDA-MPPBZ, comparative),4,4′-diamino-2,2′-bis(4-phenylphenyl)biphenyl (6FDA-3PBZ, coparative),4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (6FDA-PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)-biphenyl (6FDA-P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (6FDA-06FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (6FDA-M6FDPBZ)and 4,4′-diamino-2,2′-bis[3,5-bis(trifluoromethyl)phenyl] biphenyl(6FDA-M12FDPBZ). The results of the dielectric experiments for6FDA-based polyimides are shown in Table I, below.

TABLE I Dielectric Constants of 6FDA-based aromatic polyimide films atMHz and GHz frequency regions 2,2′-Disubstituted Diamines Groups ε = n²ε^(a) F % DCB —Cl 2.55 DMB —CH₃ 2.50 DCN —CN 2.57 DBB —Br 2.57 DIB —I2.63 PFMB —CF₃ 2.38 2.53 34.3 O6FDPBZ

2.44 2.74 25.9 M6FDPBZ

2.46 2.78 25.9 P6FDPBZ

2.43 2.67 25.9 M12FDPBZ

2.34 2.49 33.7

As shown in Table I, above, the dielectric constants for 6FDA-basedpolyimide films comprising the polymerization product of 6FDA and a4,4′-diamino-2,2′-disubstituted biphenyl selected from one of4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)-biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (O6FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (M6FDPBZ) and4,4′-diamino-2,2′bis[3,5-bis(trifluoromethyl)phenyl] biphenyl (M12FDPBZ)that are less than about 2.8.

The thermal expansion and glass transition temperatures for 6FDA-basedpolyimide films was determined by using the Thermal Mechanical Analysis(TMA) and Differential Scanning Calorimetry (DSC) methods. Thecoefficient of thermal expansion (CTE) and glass transition temperatures(Tg) for the 6FDA-based polyimide films are shown in Table II, below.

The glass transition temperatures (Tg) of the 6FDA-based polyimide filmsof the present invention were evaluated by Differential ScanningCalorimetry (DSC), using heating rate of 10° C./minute. Prior to anymeasurements, the polyimide film samples were heated to 390° C., heldfor 5 minutes, and subsequently cooled to room temperature at a rate of10° C./minute in order to avoid hysteresis effects. Relatively largequantities of samples were used in the DSC sample pans in order todetect an observable Tg. The baseline of DSC was calibrated using astandard method known in the art and the temperature range wascalibrated using Indium as the standard sample.

Thermal Mechanical Analysis (TMA) was used to evaluate the glasstransition temperatures (Tg) and coefficients of thermal expansion(CTEs) of the 6FDA-based polyimide films of the present invention. Thetemperature of TMA was calibrated using standard Indium samples underthe penetration mode according to the standard procedure known in theart. The force and measurement length range were also calibrated byknown methods in the art. In order to precisely measure the Tgs and theCTEs, the polyimide films, having thicknesses from about 10 μm to about30 μm and a 22 millimeter fixed width were heated to 300° C. undernitrogen with a 1.0 MPa annealing stress (0.5 and 1.5 MPa were alsoused) and held at this temperature for 20 minutes. After cooling to 30°C., the polyimide films were subjected to different stresses with aheating rate of 10° C./minute. The Tg was taken as the temperature atthe point of change in slope of dimensional change versus temperature.The Tgs obtained at each stress level were then extrapolated to zerostress. The CTE value was taken as the mean of the dimensional changebetween 50° C. and 150° C. The CTEs obtained at each stress level werethen extrapolated to zero stress.

TABLE II CTEs and Tgs of 6FDA-based polyimide films 2,2′-DisubstitutedCTE Tg (° C.) Tg (° C.) Diamine Groups (×10⁻⁶/° C.) (TMA) (DSC) DCB —Cl35.3 336 362 DMB —CH₃ 39.1 325 355 DCN —CN 38.3 331 357 DBB —Br 37.5 329353 DIB —I 39.0 319 350 PFMB —CF₃ 42.2 315 341 MPPBZ

49.3 286 299 O6FDPBZ

50.3 289 307 M6FDPBZ

52.2 278 288 P6FDPBZ

51.0 283 292 3PBZ

53.2 285 287 M12FDPBZ

54.1 263 282

As shown in Table II, above, the coefficients of thermal expansion(CTEs) for the 6FDA-based polyimide films comprising the polymerizationproduct of 6FDA and 4,4′-diamino-2,2′-disubstituted biphenyl selectedfrom one of 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)-biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (O6FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (M6FDPBZ) and4,4′-diamino-2,2′bis[3,5-bis(trifluoromethyl)phenyl] biphenyl (M12FDPBZ)are from about and 42.4×10−6/° C. to about 54.1×10−6/° C. The 6FDA-basedpolyimide films comprising the polymerization product of 6FDA and a4,4′-diamino-2,2′-disubstituted biphenyl having one of the2′2-disubstituted groups trifluoromethyl and trifluoromethyl substitutedphenyl at papa-, meta- and ortho-positions, exhibit improved CTEs andlower Tgs in comparison to those 6FDA-based polyimide films comprisingthe polymerization product of 6FDA and a 4,4′-diamino-2,2′-disubstitutedbiphenyls without a fluorine-containing substituent at the 2,2′positions of the diamine, which are from about 35.5×10−6/° C. to about39.0×10−6/° C.

The glass transition temperatures (Tgs) for the 6FDA-based polyimidefilms comprising the polymerization product of 6FDA and a4,4′-diamino-2,2′-disubstituted biphenyl selected from one of4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)-biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (M6FDPBZ) and4,4′-diamino-2,2′bis[3,5-bis(trifluoromethyl)phenyl] biphenyl (M12FDPBZ)were determined by the TMA and DSC methods. As shown in Table II, above,the glass transition temperatures (Tgs) for the 6FDA-based polyimidefilms comprising the polymerization product of 6FDA and a4,4′-diamino-2,2′-disubstituted biphenyl selected from one of4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (O6FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (M6FDPBZ) and4,4′-diamino-2,2′bis[3,5-bis(trifluoromethyl)phenyl] biphenyl(M12FDPBZ), as determined by TMA, is in the range of about 263° C. toabout 315° C., and as determined by DSC, is in the range of about 282°C. to about 341° C. The glass transition temperatures (Tgs) for the6FDA-based polyimide films comprising the polymerization product of a4,4′-diamino-2,2′-disubstituted biphenyl without a fluorine-containingsubstituent at the 2,2′-positions of the diamine, as determined by TMA,is in the range of about 319° C. to about 336° C., and as determined byDSC, is in the range of about 350° C. to about 362° C.

The polyimide films for the thermal stability were prepared as follows:solutions of 6FDA-based polyimides in cyclopentanone, DMAc (12% w/w),and/or m-cresol (5%) were filtered through 5 um Whatman Teflon syringefilters. The solutions were subsequently cast onto clear glasssubstrates. The thickness of the polyimide films was controlled using adoctor knife. The wet films were placed in an oven at 60° C. in order toslowly evaporate the solvent. After 24 hours, the samples were placed ina vacuum oven and dried at 180° C. for 48 hours. The film thicknessescould be control from 20 to 100 μm by this method. The resulting6FDA-based polyimide films were used for Thermogravimetric Analysis(TGA).

The 6FDA-based polyimide films prepared for TGA measurements were heatedto 300° C. and held for 20 minutes, followed by subsequent cooling to30° C. prior to measurements. The polyimide films were then heated innitrogen and air, using a heating rate of 10° C./minute and heated to650° C. 2% and 5% weight loss temperature were used to evaluate thethermal and thermo-oxidative stability of the 6FDA-based polyimidefilms. The results of the thermal and thermo-oxidative experiments, asevaluated by TGA, are shown in Table III, below.

TABLE III Temperatures for 2% and 5% weight loss in air and nitrogen for6FDA-based polyimides TGA (Air) TGA (N₂) (° C.) (° C.)2,2′-Disubstituted 2%/5% 2%/5% Diamine Groups (wt) (wt) DCB —Cl 458/497486/513 DMB —CH₃ 480/503 488/505 DCN —CN 475/513 500/528 DBB —Br 434/472457/504 DIB —I 341/413 375/467 PFMB —CF₃ 490/518 505/530 MPPBZ

425/471 440/480 O6FDPBZ

493/517 507/523 M6FDPBZ

488/508 506/525 P6FDPBZ

487/513 506/523 3PBZ

485/513 501/521 M12FDPBZ

482/509 505/525

The onset temperatures of 2% and 5% weight losses for 6FDA-basedpolyimide films are shown in Table III, above. Onset temperatures of 2%and 5% weight losses in both atmospheres are used to represent thethermal and thermo-oxidative stability of aromatic polyimides. Theresults in Table III demonstrate that 6FDA-based polyimide filmscomprising the polymerization product of 6FDA and one of4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (-6FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (M6FDPBZ) and4,4′-diamino-2,2′bis[3,5-bis(trifluoromethyl)phenyl] biphenyl (M12FDPBZ)exhibit a 2% weight loss at 425° C. to 493° C. in air and a 2% weightloss in nitrogen at 440° C. to 507° C. The results further indicate thatpolyimides comprising the reaction product of 6FDA and one of4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (PFMB),4,4′-diamino-2,2′-bis(p-trifluorometheylphenyl)-biphenyl (P6FDPBZ),4,4′-diamino-2,2′-bis(o-trifluoromethylphenyl)-biphenyl (O6FDPBZ),4,4′-diamino-2,2′-bis(m-trifluoromethylphenyl) biphenyl (M6FDPBZ) and4,4′-diamino-2,2′bis[3,5-bis(trifluoromethyl)phenyl] biphenyl (M12FDPBZ)exhibit a 5% weight loss in air at 471° C. to 518° C., and a 5% weightloss in nitrogen at 480° C. to 530° C.

The Comparative results in Table III demonstrate that 6FDA-basedpolyimide films comprising the polymerization product and one of4,4′-diamino-2,2′-dichlorobiphenyl (DCB, comparative),4,4′-diamino-2,2′-dibromobiphenyl (DBB, comparative),4,4′-diamino-2,2′-diiodobiphenyl (DIB, comparative),4,4′-diamino-2,2′-dimethylbiphenyl (DMB, comparative),4,4′-diamino-2,2′-dicyanobiphenyl (DCN, comparative),4,4′-diamino-2,2′-bis(p-methylphenyl)biphenyl (MPPBZ, comparative),4,4′-diamino-2,2′-bis(4-phenylphenyl)biphenyl (6FDA-3PBZ, comparative)experience a 2% weight loss at 341° C. to 480° C. in air and 2% weightloss in nitrogen at 375° C. to 50° C. The results in Table III furtherdemonstrate that 6FDA-based polyimide films experience 5% weight loss at413° C. to 503° C. in air and 5% weight loss at 467° C. to 528° C. innitrogen.

Several solvents were used to determine the solubility of 6FDA-basedaromatic polyimides at ambient temperature. The 6FDA-based polyimideswere considered to be soluble if a solution of 5% (wt/wt) concentrationcould be prepared. The results of the solubility experiments are shownin Table IV, below.

TABLE IV Solubility of 6FDA-based polyimides with different diaminesCyclo- Diamine Acetone pentanone THF DMAc DMF NMP DCB + + + + + +DMB + + + + + + DCN + + + + + + DBB + + + + + + DIB + + + + + +PFMB + + + + + + MPPBZ + + + + + + O6FDPBZ + + + + + +M6FDPBZ + + + + + + P6FDPBZ + + + + + + 3PBZ + + + + + +M12FDPBZ + + + + + + + Minimum solubility more than 5% (wt)

It is well known that aromatic polyimides are insoluble in manyconventional organic solvents, due to their highly conjugated, rigid-rodchemical structures, In order to employ a one-step polymerizationmethods for obtaining high molecular weight aromatic polyimides usefulas coatings, layers or films for microelectronic applications, it isnecessary to develop polyimides having a good solubility in organicsolvents. As shown in Table IV above, the 6FDA-based aromatic polyimidesare soluble in many conventional organic solvents, such as acetone,cyclopentanone, tetrahyofuran, dimethlacetamide (DMAc), N,N′-dimethylformamide (DMF) and N-methylpyrrolidone (NMP).

Without being bound by any particular theory, the unexpected solubilityof the 6FDA-based polyimides may be attributed partially to theincorporation of the twisted-biphenyl diamines. The non-coplanar diaminedisrupt the chain packing, eliminate crystallinity and interruptconjugations along the chain backbones. The resulting loose packinggenerates more free volume, which permit solvent molecules to penetrateinto the polymer systems.

The dielectric constants for PFMB-based polyimide films was determinedusing ASTM-150 method at 1 MHz on polyimide films having a thickness of10 to 40 microns. The results of the dielectric experiments forPFMB-based polyimides are shown in Table V, below.

The dielectric constants for PFMB-based polyimide films was determinedusing ASTM-150 method at 1 MHz on PFMB-based polyimide films having athickness of 10 to 40 microns. The dielectric constants for PFMB-basedpolyimide films comprising the polymerization product of PFMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(PFMB-HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M12FDPBPDA). Comparative expereiments were alsoconducted to determine the dielectric constants for PFMB-based polyimidefilms comprising the polymerization product of PFMB and one of2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride(PFMB-DPBPDA, comparative), 4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-BPDA, comparative),2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride (PFMB-DBBPDA,comparative) were also determined. The results of the dielectricexperiments for PFMB-based polyimides are shown in Table V, below.

TABLE V Dielectric constants of PFMB-based aromatic polyimide films inthe MHz and GHz frequency regions 2,2′-Disubstituted Dianhydride Groupsε = n² ε^(a) F % BPDA none 2.64 2.89 22.2 DBBPDA —Br 2.60 HFBPDA —CF₃2.37 DPBPDA

2.59 O6FDPBPDA

2.46 2.68 26.3 M6FDPBPDA

2.48 2.79 26.3 P6FDPBPDA

2.45 2.75 26.3 M12FDPBPDA

2.37 2.45 34.1 ^(a)Determined using ASTM-150 method at 1 MHz on filmwith thickness of 10–40 μm

As shown in Table V, above, the dielectric constants for PFMB-basedpolyimide films comprising the polymerization product of PFMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(PFMB-HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M6FDPBPDA),2,2′-bis-[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M12FDPBPDA) exhibit low dielectric constants, namelyless than 2.8. The PFMB based polyimide films comprising thepolymerization product of PFMB and one of2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride(PFMB-DPBPDA, comparative), 4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-BPDA, comparative),2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride (PFMB-DBBPDA,comparative) exhibit higher dielectric constants, namely greater than2.8. The results Table V indicate that the PFMB-based polyimide filmscomprising the polymerization product of PFMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(PFMB-HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M12FDPBPDA) exhibit lower dielectric constants incomparison to those PFMB based polyimide films comprising2,2′-disubstituted-4,4′5,5′-biphenyltetracarboxylic dianhydrides withoutfluorinated substituents at the 2,2′ positions.

The thermal expansion and glass transition temperatures for PFMB-basedpolyimide films was determined by using the Thermal Mechanical Analysis(TMA) and Differential Scanning Calorimetry (DSC) methods. Anon-fluorine substituent-containing diamine (DMB) was also polymerizedto the same 2,2′-disubstituted-4,4′5,5′-biphenyltetracarboxylicdianhydrides as was the diamine PFMB. The coefficient of thermalexpansion (CTE) and glass transition temperatures (Tgs) for thePFMB-based and DMB-based polyimide films are shown in Table VI, below.

The glass transition temperatures (Tg) of the PFMB-based and DMB-basedpolyimide films of the present invention comprising the polymerizationproduct of PFMB or DMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride ((O6FDPBPDA)),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M6FDPBPDA), 2,2′-bisp-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylic dianhydride(P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M12FDPBPDA). Comparative experiments were also conducted todetermine the glass transition temperatures (Tgs)for PFMB-based andDMB-based polyimide films comprising the polymerization product of PFMBor DMB and one of 2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylicdianhydride (DPBPDA, comparative), 4,4′,5,5′-biphenyltetracarboxylicdianhydride (BPDA, comparative),2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DBBPDA),comparativewere evaluated. Thermal Mechanical Analysis (TMA) was used toevaluate the glass transition temperatures (Tg) and coefficients ofthermal expansion (CTEs) of the PFMB-based and DMB-based polyimide filmsof the present invention. The temperature of TMA was calibrated usingstandard Indium samples under the penetration mode according to thestandard procedure known in the art. The force and measurement lengthrange were also calibrated by known methods in the art. In order toprecisely measure the Tgs and the CTEs, the polyimide films, havingthicknesses from about 10 μm to about 30 μm and a 22 millimeter fixedwidth were heated to 300° C. under nitrogen with a 1.0 MPa annealingstress (0.5 and 1.5 MPa were also used) and held at this temperature for20 minutes. After cooling to 30° C., the polyimide films were subjectedto different stresses with a heating rate of 10° C./minute. The Tg wastaken as the temperature at the point of change in slope of dimensionalchange versus temperature. The Tgs obtained at each stress level werethen extrapolated to zero stress. The CTE value was taken as the mean ofthe dimensional change between 50° C. and 150° C. The CTEs obtained ateach stress level were then extrapolated to zero stress.

The thermal expansion and glass transition temperatures for PFMB-basedand DMB-based polyimide films was determined by using the TMA method.The coefficients of thermal expansion (CTEs) and glass transitiontemperatures (Tgs) for the PFMB-based and DMB-based polyimide films areshown in Table VI, below.

TABLE VI CTEs and Tgs for PFMB-based and DMB-based polyimide films 2,2′-CTE CTE Disubstituted (×10⁻⁶/° C.) Tg (° C.) (×10⁻⁶/° C.) Tg (° C.)Dianhydride Groups (PFMB-) (PFMB-) (DMB-) (DMB-) BPDA none 7.06 304 1.26334 DBBPDA —Br 13.4 330 10.5 337 HFBPDA —CF₃ 23.2 332 18.5 345 DPBPDA

25.8 346 24.9 364 O6FDPBPDA

32.0 372 26.5 369 M6FDPBPDA

32.7 342 30.6 346 P6FDPBPDA

34.5 356 33.3 367 M12FDPBPDA

38.3 339 36.9 342

As shown in Table VI, above, the coefficient of thermal expansion (CTE)for the PFMB-based polyimide films comprising the polymerization productof PFMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M12FDPBPDA) are in the range of about 23.2×10⁻⁶/° C. toabout 38.3×10⁻⁶/° C., while the coefficient of thermal expansion (CTE)for the PFMB-based polyimide films comprising the polymerization productof PFMB and one of 2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylicdianhydride (DPBPDA, comparative), 4,4′,5,5′-biphenyltetracarboxylicdianhydride (BPDA, comparative),2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DBBPDA), arein the range of about 7.06×10⁻⁶/° C. to about 25.8×10⁻⁶/° C.

The coefficient of thermal expansion (CTE) for the DMB-based polyimidefilms comprising the polymerization product of DMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride ((O6FDPBPDA)),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M12FDPBPDA) are in the range of about 18.5×10⁻⁶/° C. toabout 36.9×10⁻⁶/° C., while the coefficient of thermal expansion (CTE)for the DMB-based polyimide films comprising the polymerization productof DMB and one of 2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylicdianhydride (DPBPDA, comparative), 4,4′,5,5′-biphenyltetracarboxylicdianhydride (BPDA, comparative),2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DBBPDA), arein the range of about 1.26×10⁻⁶/° C. to about 24.9×10⁻⁶/° C.

The glass transition temperature (Tg) PFMB-based polyimide filmscomprising the polymerization product of PFMB and one of2,2′-bis(trifluoromethyl)4,4′,5,5′-biphenyltetracarboxylic dianhydride(HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M6FDPBPDA), 2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylic dianhydride (P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M12FDPBPDA) are in the range of about 332° C. to about 372°C., while the glass transition temperature (Tg) for the PFMB-basedpolyimide films comprising the polymerization product of PFMB and one of2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DPBPDA,comparative), 4,4′,5,5′-biphenyltetracarboxylic dianhydride (BPDA,comparative), 2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride(DBBPDA), are in the range of about 304° C. to about 346° C.

The glass transition temperature (Tg) for the DMB-based polyimide filmscomprising the polymerization product of DMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]4,4′,5,5′-biphenyltetracarboxylicdianhydride (M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M12FDPBPDA) are in the range of about 345° C. to about 369°C., while the glass transition temperature (Tg) for the DMB-basedpolyimide films comprising the polymerization product of DMB and one of2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DPBPDA,comparative), 4,4′,5,5′-biphenyltetracarboxylic dianhydride (BPDA,comparative), 2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride(DBBPDA), are in the range of about 334° C. to about 364° C.

The thermal and thermo-oxidative stability of PFMB-based aromaticpolyimide films was evaluated by nonisothermal TGA experiments under drynitrogen and air. The results of the thermal and thermo-oxidativeexperiments are shown in Table VII, below.

TABLE VII Temperatures for 2% and 5% weight loss in air and nitrogen forPFMB-based polyimides TGA (Air) TGA (N₂) 2,2′-Disubstituted (° C.) (°C.) Dianhydride Groups 2%/5% (wt) 2%/5% (wt) BPDA none 531/564 530/565DBBPDA —Br 486/518 492/523 HFBPDA —CF₃ 530/549 537/566 DPBPDA

498/539 513/542 O6FDPBPDA

529/553 531/559 M6FDPBPDA

529/563 536/566 P6FDPBPDA

524/546 534/555 M12FDPBPDA

530/550 535/565

The onset temperatures of 2% and 5% weight losses for PFMB-basedpolyimide films comprising the polymerization product of PFMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(PFMB-HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-M12FDPBPDA). Comparative expereiments were alsoconducted to determine the dielectric constants for PFMB-based polyimidefilms comprising the polymerization product of PFMB and one of2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride(PFMB-DPBPDA, comparative), 4,4′,5,5′-biphenyltetracarboxylicdianhydride (PFMB-BPDA, comparative),2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride (PFMB-DBBPDA,comparative) are shown in Table VII, above. Onset temperatures of 2% and5% weight losses in both atmospheres are used to represent the thermaland thermo-oxidative stability of aromatic polyimides. The results inTable VII demonstrate that PFMB-based polyimide films comprising thepolymerization product of PFMB and one of2,2′-bis(trifluoromethyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride(HFBPDA),2,2′-bis[o-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (O6FDPBPDA),2,2′-bis[m-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M6FDPBPDA),2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (P6FDPBPDA) and2,2′-bis[3,5-bis(trifluoromethyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylicdianhydride (M12FDPBPDA) experience a 2% weight loss weight loss atabout 524° C. to 530° C. in air, and at about 531° C. to about 537° C.in nitrogen, respectively. These compounds experience a 5% weight lossat 549° C. to 563° C. in air, and at about 555° C. to about 566° C. innitrogen. The results further show that PFMB-based polyimide filmscomprising the polymerization product of PFMB and one of2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DPBPDA,comparative), 4,4′,5,5′-biphenyltetracarboxylic dianhydride (BPDA,comparative), 2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic dianhydride(DBBPDA, comparative) experience a 2% weight loss weight loss at about486° C. to 531° C. in air, and at about 492° C. to about 530° C. innitrogen, respectively. These polyimides exhibit a 5% weight loss atabout 518° C. to about 564° C. in air, and at about −542° C. to 556° C.

Several solvents were used to determine the solubility of PFMB-basedaromatic polyimides at ambient temperature. These polyimides areprepared by the 2,2′-disubsitution groups on4,4′,5,5′-biphenyltetracarboxylic dianhydrides in polyimide backbones.The polyimides were considered to be soluble if a solution of 5% (wt/wt)concentration could be prepared. The results of the solubilityexperiments are shown in Table VIII, below.

TABLE VIII Solubility of PFMB-based polyimides with differentdianhydrides Cyclo- m- p-chloro Dianhydride Acetone pentanone THF NMPcresol phenol BPDA − − − − + + DBBPDA + + + + + + HFBPDA + + + + + +DPBPDA + + + + + + O6FDPBPDA + + + + + + M6FDPBPDA + + + + + +P6FDPBPDA + + + + + + M12FDPBPDA + + + + + + + Minimum solubility morethan 5% (wt) − Maximum solubility less than 2% (wt)

As shown in Table VIII above, the PFMB-based aromatic polyimides aresoluble in many conventional organic solvents, such as acetone,cyclopentanone, tetrahyofuran, N-methylpyrrolidone (NMP), m-cresol andp-chlorophenol. The experimental results shown in Table VIIIdemonstrate, with the exception of BPDA-PFMB which contains the4,4′,5,5′-bipohenyltetracarboxylic dianhydride (BPDA) withoutdisubstituted groups at the 2,2′-positions, that the solubility of theresulting polyimides can be improved through the use of2,2′-disubstituted-4,4′,5,5′-biphenyltetracarboxylic dianhydrides inpolyimide backbones.

Several solvents were used to determine the solubility of DMB-basedaromatic polyimides at ambient temperature. These polyimides areprepared by the 2,2′-disubsitution of pendant groups on4,4′,5,5′-biphenyltetracarboxylic dianhydrides in polyimide backbones.The polyimides were considered to be soluble if a solution of 5% (wt/wt)concentration could be prepared. The results of the solubilityexperiments are shown in Table IX, below.

TABLE IX Solubility of DMB-based polyimides with different dianhydridesCyclo- m- p-chloro Dianhydride Acetone pentanone THF NMP cresol phenolBPDA − − − − − + DBBPDA − + + + + + HFBPDA − − + + + + DPBPDA −− + + + + O6FDPBPDA − − + + + + M6FDPBPDA − − + + + + P6FDPBPDA −− + + + + M12FDPBPDA + − + + + + + Minimum solubility more than 5% (wt)− Maximum solubility less than 2% (wt)

As shown in Table IX above, the DMB-based aromatic polyimide BPDA-DMB isonly soluble in p-chlorophenol. The DMB-based polyimide M12FDPBPDA-DMBis soluble in soluble in many conventional organic solvents, such asacetone, cyclopentanone, tetrahyofuran, N-methylpyrrolidone (NMP),m-cresol and p-chlorophenol The DMB-based polyimides DBBPDA-DMB,HFBPDA-DMB DPBPDA-DMB, (O6FDPBPDA)-DMB, M6FDPBPDA-DMB and P6FDPBPDA arenot soluble in acetone, but are soluble in cyclopentanone,tetrahyofuran, N-methylpyrrolidone (NMP), m-cresol and p-chlorophenolThe experimental results shown in Table IX demonstrate, with theexception of BPDA-DMB which contains the4,4′,5,5′-bipohenyltetracarboxylic dianhydride (BPDA) withoutdisubstituted groups at the 2,2′-positions, that the solubility of theresulting polyimides can be improved through the use of2,2′-disubstituted-4,4′,5,5′-biphenyltetracarboxylic dianhydrides inpolyimide.

The polyimide coatings of this invention have excellent dielectricconstants, coefficients of Thermal expansion, and thermal stability.Additionally, the polyimides used in this invention are advantageouslysoluble in common organic solvents and, therefore, are easily processedand used for Insulating electronic and microelectronic components.

Based on the foregoing disclosure, it is therefore demonstrated that theobjects of the present invention are accomplished by the polyimidecoating compositions and coated integrated circuit chips describedherein. It should be understood that the selection of specific organicsubstituents (i.e. —R groups) of the aromatic dianhydrides and aromaticdiamines, polymerization techniques, polymerization conditions, andmethods of coating integrated circuit chips can be determined by onehaving ordinary skill in the art without departing from the spirit ofthe invention herein disclosed and described. It should therefore beappreciated that the present invention is not limited to the specificembodiments described above, but includes variations, modifications andequivalent embodiments defined by the following claims.

1. An insulated integrated circuit comprising: an integrated circuit;and an insulating layer having a dielectric constant of less than about2.5 is disposed on said integrated circuit, wherein said insulatinglayer is a polyimide film that is the polymerization product of anaromatic diamine having the general formula (I):

and an aromatic dianhydride having the formula (II):

wherein R is an organic substituent selected from the group consistingof CF₃, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5 bis[(m-trifluoromethyl) phenyl]; or thepolymerization product of an aromatic dianhydride having the generalformula (III):

and an aromatic diamine having the formula (IV):

wherein R is a substituent selected from the group consisting oftrifluoromethyl, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5′-bis[(m-trifluoromethyl) phenyl]. 2.The insulated integrated circuit according to claim 1, wherein saidintegrated circuit is a microprocessor.
 3. The insulated integratedcircuit according to claim 1, wherein the thickness of said insulatinglayer is from about 10 to about 1000 microns.
 4. The insulatedintegrated circuit according to claim 1, wherein the thickness of saidinsulating layer is from about 10 to about 500 microns.
 5. The insulatedintegrated circuit according to claim 1, wherein the thickness of saidinsulating layer is from about 10 to about 100 microns.
 6. The insulatedintegrated circuit according to claim 1, wherein the coefficient ofthermal expansion is greater than about 23×10⁻⁶/° C.
 7. The insulatedintegrated circuit according to claim 1, wherein the coefficient ofthermal expansion is greater than about 42×10⁻⁶/° C.
 8. The insulatedintegrated circuit according to claim 1, wherein the coefficient ofthermal expansion is greater than about 50×10⁻⁶/° C.
 9. An insulatedelectrically conductive component comprising: an electrically conductivecomponent; and an insulating layer comprising the polymerization productof an aromatic diamine having the general formula (I):

and an aromatic dianhydride having the formula (II):

wherein R is an organic substituent selected from the group consistingof CF₃, O-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5-bis[(m-trifluoromethyl) phenyl]; or thepolymerization product of an aromatic dianhydride having the generalformula (III):

and an aromatic diamine having the formula (IV):

wherein R is a substituent selected from the group consisting oftrifluoromethyl, o-trifluoromethyl phenyl, m-trifluoromethyl phenyl,p-trifluoromethyl phenyl and 3,5′-bis[(m-trifluoromethyl) phenyl], andwherein the coefficient of thermal expansion of the insulatedelectrically conductive component is greater than about 23×10⁻⁶/° C. 10.The insulated electrically conductive component according to claim 9,wherein said electrically conductive component is selected from thegroup consisting of capacitors, diodes, connectors and transistors. 11.The insulated electrically conductive component according to claim 9,wherein the thickness of said insulating layer is from about 10 to about1000 microns.
 12. The insulated electrically conductive componentaccording to claim 9, wherein the thickness of said insulating layer isfrom about 10 to about 500 microns.
 13. The insulated electricallyconductive component according to claim 9, wherein the thickness of saidinsulating layer is from about 10 to about 100 microns.
 14. TheInsulated electrically conductive component according to claim 9,wherein the dielectric constant of said insulating layer is less thanabout 2.8.
 15. The insulated electrically conductive component accordingto claim 9, wherein the dielectric constant of said insulating layer isless than about 2.7.
 16. The insulated electrically conductive componentaccording to claim 9, wherein the dielectric constant of said insulatinglayer is less than about 2.5.
 17. The insulated electrically conductivecomponent according to claim 9, wherein the coefficient of thermalexpansion is greater than about 42×10⁻⁶/° C.
 18. The insulatedelectrically conductive component according to claim 1, wherein thecoefficient of thermal expansion is greater than about 50×10⁻⁶/° C.